why did my record player slow down, speed up, then go back to normal?

@stereo5 thanks for the tip! i'm going to do that, even if the belt isn't the problem. (it probably is, but then again, it only happened once for about 30 seconds.)

hey guys. thanks for all the responses! it is a belt drive, and i was about 25 minutes into one side of a record (CSNY's 4 way street, side 3, southern man, in case anyone wants to know). It was kind of a humid day. This has only happened once.

thanks again everyone. any input helps.

@atmasphere thanks. this is an older turntable, but it has electronic speed buttons (33, 45 rpm). I think i'll check the buttons for corrosion.

i guess it could have been a power surge from what everyone is saying. It might've been the belt, but it had never happened before or since. 

@millercarbon 

man you are funny! you have kept on talking about aliens throughout the post. i don't care if you keep going, i like having you around.

I actually went to play a record today, and I had to press the (electronic) buttons multiple times before it did its function. There was no speed swell, though.

I am thinking that the buttons are corroded. 
Also, @stereo5 I did the talcum powder thing today. Thanks again for the tip!